vim: Update :set (#27805)

Update VimSet commands to better match the other commands by displaying
the leading `:`:

|Before|After|
|--|--|

|![image](https://github.com/user-attachments/assets/1bc21a06-e71f-4e40-90a7-ffdd903fd7b5)|![image](https://github.com/user-attachments/assets/df59279f-d454-4701-8330-2529506850cd)|


Release Notes:

- N/A

crates/vim/src/command.rs

@@ -92,7 +92,7 @@ impl VimOption {
 
                 CommandInterceptResult {
                     string: format!(
-                        "set {}",
+                        ":set {}",
                         options.iter().map(|opt| opt.to_string()).join(" ")
                     ),
                     action: VimSet { options }.boxed_clone(),